The invention relates to an arrangement for encoding two-dimensional information grouped in periodical information clusters of the picture type, which arrangement comprises
(a) a variable length encoding stage;
(b) a reconstruction stage coupled to the encoding stage and adapted to carry out on the signals present at its junction point with the encoding stage the inverse operations of those already carried out at the junction point on the input signals of said encoding stage;
(c) a stage for estimating the movement per block bounded within the information clusters; and
(d) a stage for prediction based on the output signals of the reconstruction and movement estimation stages.
The invention also relates to an arrangement for decoding signals previously transmitted and/or stored after rate reduction of the original signals, which are representative of two-dimensional information initially grouped in periodical information clusters of the picture type in successively odd and even rows and accompanied by first movement information components related to the relative movement of the information clusters among themselves, having been encoded before transmission and/or storage in an encoding arrangement comprising:
(a) a variable length encoding stage;
(b) a reconstruction stage connected in parallel in the encoding stage and adapted to carry out on the signals present at its junction point with the encoding stage the inverse operations of those already carried out at the junction point on the input signals of the encoding stage;
(c) a stage for estimating the movement by means of limited blocks within the information clusters, adapted to receive a series of input signals of a specific row from the encoding arrangement and first information components relating to the movement between these signals and, with respect to the input signals, being representative of non-transmitted complementary signals of the opposite row, and adapted to supply from these signals and information components second movement information components which in the series of input signals are representative of an input signal which follows a previous input signal;
(d) a stage for prediction based on the output signals of the reconstruction and movement estimation stages;
(e) a stage for selecting from the input signals of the encoding arrangement on the one hand and from the output signals of the prediction stage on the other hand signals to be encoded in the encoding stage;
the decoding arrangement comprising a decoding stage which comprises a series arrangement of a buffer memory, a decoding circuit and a circuit for inverse quantising an orthogonal transform of decoded signals, receiving also signals C and N previously transmitted and/or stored and constituting classification information of blocks in accordance with their contents and normalization information, respectively.
This invention is particularly used in the case where the two-dimensional information represents animated pictures and where a compact disc is used to support this information.
The transmission and/or storage of a very large quantity of information, associated, for example with pictures, generally implies that the signals to be transmitted and/or stored must be compressed, i.e. their number must be reduced at a rate to be defined. The reduction rate is defined inter alia by the fact that a sufficient quantity of signals should be preserved so as not to degrade the general information which they carry, for example, (within the scope of the cited application) by the fact that an acceptable picture quality should be maintained.
The majority of currently known encoding processes for realizing this reduction rate are based on orthogonal transforms of the discrete cosine transform type which enable a rate reduction of the order of 10 to 1. An example of such transforms is described in U.S. Pat. No. 4,394,774. However, this ratio is not sufficient for a number of applications such as, for example, the storage and treatment of images on a compact disc.
Prior European Patent Application No. 90201554.4 in the name of the applicant describes an arrangement for processing signals realizing complementary reduction in a ratio of 2 to 1. This arrangement is adapted to be included in general in a system for transmitting and/or storing signals which are regrouped in periodical clusters such as pictures, which system comprises a transmission stage and, after transmission and/or storage of the signals transmitted on a carrier having a limited passband necessitating the rate reduction treatment, a stage for receiving and/or reading the transmitted and/or stored signals. The relevant processing circuit itself essentially includes the following sub-assemblies:
(a) a sub-assembly for temporal sub-sampling in a specific ratio for supplying in accordance with a first transmission and/or storage mode, referred to as compensated mode, a first series of signals to be transmitted and/or stored at a frequency which is lower than that of the clusters of original signals;
(b) a sub-assembly for estimating the movement between blocks relating to successive periodical clusters for supplying per block a movement information to be transmitted and/or stored, replacing those blocks which are eliminated by said temporal sub-sampling operation;
(c) a reconstruction sub-assembly using movement compensation for supplying on the one hand from those blocks which in the original signals lead to the transmission and/or storage in accordance with the compensated mode and on the other hand from the movement information associated with said blocks replacing the eliminated blocks, the blocks of signals such as they are reconstructed at the reception side as a substitute for the eliminated blocks and from the series of transmitted signals and movement information;
(d) a decision-making sub-assembly for supplying for each block from a comparison involving the original signals and the signals reconstructed after movement compensation, information on choosing or not choosing the compensated mode in accordance with the result of this comparison;
(e) a sub-assembly for fall-back treatment for associating per block with the first series of signals in accordance with a second mode referred to as fall-back mode of transmitting and/or storing as a function of the result of the comparison, replacing the first compensated mode, at least one second series of signals which is synchronous with the first series.